Many human tumors can be transplanted and passaged in the athymic mice retaining most of their original properties. The rapid growth of some of these tumors provides large amounts of tumor material for biochemical isolation procedures which previously have not been available. The objective of the proposed research is to study the membrane-bound ATPases of these tumor cells, specifically an astrocytoma, an oat cell carcinoma and several melanomas. Our study indicated that the mitochondrial ATPases from these human tumors respond to uncouplers, such as dinitrophenol and carbonylcyanide chlorophenylhydrazone in a manner different from mitochondria or a normal tissue such as liver. Mitochondria from these tumors exhibited various degrees of coupling. These tumor cells also possess large amounts of ATPase activity associated with the microsomal and plasma membranes, the significance of these activities in the overall physiology of the cells not being known. I propose to study these enzymes first in their native membranes which can be obtained by subcellular fractionation of the tumor homogenates. This is most important for the mitochondrial ATPases. Other features peculiar to the tumor mitochondria will only be revealed by investigating the functions of the whole mitochondria such as nucleotide, substrate and ion transport. The possibility of the active microsomal and plasma membrane ATPases being involved in ATP driven transport processes shall also be investigated. Further purification will be attempted with the aid of detergent and other methods applicable to isolation of membrane proteins. The purified ATPases will be characterized with regard to their enzymatic properties and molecular structures. I hope such basic information will provide an understanding of their biological functions and the means by which they affect energy metabolism and ion fluxes in human tumor cells.